WifiManager: add updateInterfaceIpState

Add a call to WifiManager that allows ConnectivityService to
provide interface mode change updates.  Mode variables are also
added in this CL.

A corresponding CL will be added to WifiServiceImpl.

Fixed two checkstyle errors on imports.

Bug: 31466854
Test: make
Change-Id: Iccccd2643515a09fadb29f7b7e82697aaf994189